Any discussion of document, devices, acts or knowledge in this specification is included to explain the context of the invention. It should not be taken as an admission that any of the material forms a part of the prior art base or the common general knowledge in the relevant art in Australia or elsewhere on or before the priority date of the disclosure and broad consistory statements herein.
In the United States alone, nearly two million people suffer from various neuromuscular disorders where control of limbs is severely impaired. In many of these patients, however, the portion of the brain responsible for movement remains intact, and it is disease and trauma to the spinal cord, nerves and muscles that limit mobility, function and independence. For these people, the ability to restore lost control at even a rudimentary level could lead to a greatly improved quality of life.
At present, there are two primary options for restoring function. One option is to increase the capabilities of the remaining pathways, substituting paralyzed or amputated muscles with those under voluntary control. While this method has been highly successful for amputees by re-innervating forearm nerves into abdominal muscles which control a bionic arm, the restored function greatly depends on the site of damage or condition, with people paralyzed by brainstem or high cervical injuries only able to achieve minor functional improvement. A second option is to provide the brain with a new communication and control channel to convey messages to the external world. Currently, these brain controlled interfaces (BCIs) measure electroencephalographic or other electrophysiological activity via surgically implanted epidural, subdural, and intracortical electrodes. While cortical measurements performed with electrodes placed on the scalp enable non-invasive neuronal measurements, they require daily application and are prone to noise and movement related artefacts. Penetrating and non-penetrating intracranial electrodes, implanted after a craniotomy directly onto the surface of a cortical area, have much better signal to noise ratios (relative to scalp electrodes) and have been shown to enable rudimentary prosthetic hand operation. These methods, however, require invasive surgery and carry a relatively high risk of complication, which can involve infections and bleeding. Furthermore, craniotomies are limited in access to the central nervous system, with many motor and sensory cortex areas hidden and inaccessible within cortical folds. These approaches are restricted in position and cannot be relocated once implanted and are subject to signal deterioration due to glial scar formation surrounding penetrating electrodes.
Thus, there remains a need to record and stimulate from cortical tissue in a method which is minimally invasive whilst also ensuring longevity and efficacy of recorded and induced signals.
By using blood vessels as a conduit to the brain, the risks associated with craniotomies, and the invasive creation of a burr hole in the skull of the patient is removed whilst also removing current noise and movement related artefacts observed with non-invasive scalp electrodes. Despite the minimally invasive benefits provided by these types of procedures, it is preferable that thrombus formation caused by the blockage of blood flow through a vessel is prevented. It is also preferable that the electrical energy delivered to the electrodes be as efficient as possible, which will reduce the burden placed on the electrical circuitry. Optimization of wireless telemetry aimed to send power and data directly through the body to the implanted device, will enhance device functionality and negate the risk of infection caused through lead wires creating a direct passage between the vessel and the external environment. The ability to implant coils inside blood vessels will similarly reduce surgical risks associated with perforated vasculature.
Thus, there remains a need to provide improved intravascular electrodes, telemetry circuitry and implantation positions that are capable of more efficiently transmitting and receiving electrical energy between vessels and external circuitry, while minimizing the occlusion of blood flow.
It is generally desirable to overcome or ameliorate one or more of the above mentioned difficulties, or at least provide a useful alternative.